It looks like it has nearly identical specs to the Foxconn NF4K8MC-ERS, right down to the lack of S/PDIF rear panel audio output. That's too bad. I think that's my biggest problem with the Foxconn.
Item 7 on Internal I/O Conectors says it has a "S/PDIF input/ output connector". My largest gripe is that it doesn't have gigabit lan, but that's a minor quibble since I wouldn't be using it anyways. The nice thing that pops up for me is that the socket is closer to the center of the board. That may make my HT-101 compatible with X-Qpack. It's also nicer than the Foxconn in that it has the PCIe-16 slot in the "right" place (top most) and slots for 4 DIMMs.
As for the "4x", from a GamePC review of its big brother
After scouring through Gigabyte's manuals and using the board for over a week now, the only difference we can find between a standard nForce4 and the nForce4-4x is the intended HyperTransport link speed. There were rumors floating around when the nForce4 was first being developed in that it could not run at full (5x / 1000 MHz) HyperTransport link speeds, but instead could only run at 4x / 800 MHz speeds. Our estimations were all but confirmed in the manual, where as the peak HyperTransport link speed is listed at 800 MHz, with no mention of 1000 MHz speeds.
What is likely the scenario here is that the nForce4-4x is an early batch of nForce4 chips which did not complete qualification testing at full 5x HyperTransport frequencies, thus, the nForce4-4x is likely a "binned-down" nForce4 chipset. While the rest of the chipset appears to be fully functional, this aspect may mean that Gigabyte cannot sell the chip as a "full" nForce4 chipset, which is why they may have added the 4x moniker. As you can see, nVidia has actually gone ahead and labeled the chip itself as a nForce4-4x, this is not a Gigabyte-created term.